1. Field of the Invention
This invention relates generally to an overvoltage protection circuit for a pair of telephone lines and similar data communication channels and, more particularly, to circuitry for filtering noise and transient voltage signals above data signals on the lines or channels.
2. Prior Art
Various arrangements have been used for protecting telephone and communications equipment against hazardous voltages due to lightning or power surges. However, conventional arrangements are effective for clamping transient voltages at a rated potential selected above the ring signal of conventional communications systems. The typical ring signal is about 170 volts AC peak with a frequency between 15 and 30 hertz so that the conventional arrangements typically have a rated clamping voltage of approximately 200 volts. Consequently, such arrangements are ineffective for filtering noise and transient voltage signals occurring below this standard clamping voltage.